1. Field of the Invention
The present invention relates to a steered shaft support structure.
2. Description of the Related Art
For steering systems of automobiles, a rack bushing has been proposed which supports a rack shaft serving as a steered shaft such that the rack shaft can reciprocate in a housing (see, for example, Japanese Patent Application Publication No. 2013-142451 (JP 2013-142451 A)). In general, each end of the rack shaft protruding from a corresponding one of ends of the housing is covered with and protected by a corresponding one of boots whose one end is fitted to the outside of the end of the housing. With a motion of the rack shaft in an axial direction, one boot is expanded and the other boot is contracted. The expansion and contraction of the boots increase and decrease pressure of the interior of the boots. This causes air to flow between one end and the other end of a rack bushing, generating an abnormal noise like a whistling noise.
For this reason, one technique has been proposed which provides an axial groove formed in an inner periphery of a rack bushing and extending from one end to the other end of the rack bushing (see, for example, Japanese Patent Application Publication No, 2004-183780 (JP 2004-183780 A)).
In JP 2004-183780 A, the rack bushing is provided, on one end of the rack bushing, with a flange portion extending outward in a radial direction. The flange portion is engaged with a step portion of the inner periphery of a housing, and thus the rack bushing is positioned in an axial direction. Since the flange portion is in contact with the step portion of the inner periphery of the housing, almost no air flows through an outer periphery side of the rack bushing (that is, between the rack bushing and the housing). Consequently, the air flows only through an inner periphery side of the rack bushing (that is, between the rack bushing and the rack shaft). Since a cross-sectional area for the air flow is small, the occurrence of the abnormal noise may not be prevented.